1. Field of the Invention
The present invention relates to .alpha.-cyanoacrylate adhesive composition of matter for improvement of initial adhesion strength and set time.
2. Prior Art
.alpha.-cyanoacrylate being conventionally used as adhesive composition of matter represented by a general formula EQU CH.sub.2 .dbd.C(CN)--COOR'
(where R' represents alkyl group, alkenyl group, aralkyl group, haloalkyl group, dicyclohexyl group, phenyl group et cetera with a carbon number of not more than 16) has property susceptible to anionic polymerization and liable to be polymerized to set within a short time of several seconds.about.several minutes at normal temperature through the action of various anion active substances such as water adhering to the surface of a solid substance, humidity in the atmosphere and other alkaline substances even in the absence of any catalyst. It has, therefore, hitherto been widely used as a material of instantaneous adhesives for industrial, medical and general household uses.
The .alpha.-cyanoacrylate adhesive, however, has a defect of its set time getting markedly longer if the surface to be adhered should be acidic or the quantity of water should be too small and, when the materials to be adhered are such as wooden articles, zinc chromate-plated steel plates, polyester, bakelite or EPDM, the set time is unduly long and the adhesion strength is too low.
As a prior art for improving the initial adhesion strength of .alpha.-cyanoacrylate adhesives has been known a method of using a polyalkyl ether (metha)acrylate-type plasticizer in combination with polyhydroxyphenyl carboxylic acid ester, pyrogallol or the like (Japanese Patent Publication No. 26513/1985, Japanese Patent Publication No. 41668/1989), but there was still to be desired about the set time and the initial adhesion strength strength attainable with the aforementioned difficult-to-adhere materials, this being an important problem still to be solved.